A method for preparing foamed epoxy resin prepreg

Abstract

The invention discloses a method for preparing a foamed epoxy resin prepreg, wherein the preparation method first disperses unfoamed hollow microspheres in an aqueous acrylic emulsion, then mixes and heats with an emulsion glass fiber chopped strand mat until foaming, obtains a foamed emulsion glass fiber chopped strand mat, mixes a liquid epoxy resin with a solid epoxy resin and impregnates the foamed emulsion glass fiber chopped strand mat, and prepares a foamed epoxy resin prepreg. Compared with a traditional process, the foamed epoxy resin prepreg prepared by the invention avoids the epoxy resin curing caused by excessively high foaming temperature after the hollow microspheres are mixed with the epoxy resin, so a large number of microspheres can be added to reduce the material density, and the chopped fibers are uniformly distributed in an unoriented manner, reducing the anisotropy of the material, so the prepared composite material has better comprehensive performance.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a method for preparing a foamed epoxy resin prepreg. Background Art

[0002] Epoxy resin refers to an organic polymer compound containing two or more epoxy groups in the molecule, with a relatively low molecular weight, and is a thermoplastic resin. Epoxy resin can undergo cross-linking reactions with a variety of curing agents, and the resulting thermosetting resin is a polymer with good adhesion, thermal stability, mechanical properties and dielectric properties, and has a small shrinkage rate during the preparation process, good product dimensional stability, and can maintain stable performance in most chemical solvents including alkaline solvents. It is one of the most widely used matrices in polymer-based composite materials. Fiber is a commonly used reinforcement in epoxy resin-based composite materials, such as carbon fiber, glass fiber, polyester fiber, etc. Fiber as a reinforcement can effectively improve the strength, stiffness and fatigue resistance of the composite material. In addition, it can also enable the material to obtain excellent comprehensive properties such as good corrosion resistance, formability and structural dimensional stability, so that the material has a wide range of application prospects in the fields of aerospace, transportation, energy generation, biomedical devices, etc. Prepreg is an intermediate material for preparing resin-based composite materials. It is usually a combination of matrix and reinforcement made by impregnating the matrix in reinforcing fibers. It can improve the strength, hardness, fatigue resistance, impact resistance and corrosion resistance of the composite material. Therefore, its quality will directly affect the performance of the composite material. When used, the prepreg can be directly heated and cured to form a resin-based composite material without the need to be impregnated with the matrix again. Therefore, it has the advantages of convenient use, good product stability, low porosity, etc., and has an important application position in the preparation of resin-based composite materials. With the rapid development and wide application of resin-based composite materials, many preparation methods of prepreg have also been developed, such as wet method, dry method, powder method, etc. Different preparation methods have their own advantages and disadvantages. The existing more mature process usually uses foamed expanded microspheres mixed with epoxy resin to prepare a film, and then impregnates with fibers to prepare prepreg. The disadvantage of this process is that only foamed microspheres can be used, and too high foaming temperature will cause the epoxy resin to solidify, resulting in uneven fiber dispersion, affecting the performance of the composite material. Therefore, it is necessary to further develop a more perfect prepreg preparation method. Summary of the invention

[0003] Technical problem to be solved: The technical problem to be solved by the present invention is to provide a method for preparing a foamed epoxy resin prepreg.

[0004] Technical solution: A method for preparing a foamed epoxy resin prepreg, comprising the following steps: S1. The unfoamed hollow microspheres and aqueous acrylic acid are added to water, and dispersed by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immersing the chopped glass fibers in the aqueous emulsion prepared in S1, rolling out the excess emulsion and drying, heating the hollow microspheres to rapidly foam, and obtaining a foamed emulsion glass fiber chopped mat; S3. The curing agent and accelerator are added to the liquid epoxy resin, ground and dispersed evenly, the liquid epoxy resin and the solid epoxy resin are mixed in proportion and heated to dissolve, and the liquid epoxy resin with a curing agent and accelerator is added and mixed evenly; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Preferably, in step S1, the mass ratio of water, aqueous acrylic acid and hollow microspheres is 100:10-50:20-100. Preferably, the heating temperature in step S2 is 160-180°C. Preferably, the curing agent in step S3 is dinitrile amide, and the accelerator is organic urea. Preferably, the heating and dissolving temperature in step S3 is 70-90°C. Preferably, in step S3, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:50-150. Preferably, the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat in step S4 is 100:50-200. Beneficial effects: Compared with the prior art, the present invention has the following characteristics: The foamed epoxy resin prepreg of the present invention combines the excellent properties of epoxy resin with the random distribution of chopped fibers and the lightweight characteristics of foaming technology. Compared with the traditional prepreg preparation method, the present invention can add a large number of microspheres to the epoxy resin matrix, thereby significantly reducing the material density. At the same time, the chopped fibers have better dispersion and can be evenly distributed in a random manner. Therefore, the prepared composite material has better comprehensive performance. Fiber-reinforced resin-based composite materials have the characteristics of low density, high specific strength, high temperature resistance and fatigue resistance, and have a wide range of applications. Prepreg is an intermediate material for the preparation of resin-based composite materials. It has the advantages of easy use, environmentally friendly molding process, precise resin content, and controllable product size. It plays a vital role in the preparation of resin-based composite materials, and the quality of prepreg has an important influence on the performance of resin-based composite materials. Depending on the resin matrix, prepregs based on epoxy resin are classified as thermosetting prepregs, which have the characteristics of low viscosity, easy impregnation, and low curing temperature (below 200°C). Therefore, there are many types of products and the preparation process is relatively mature. There are two main methods for preparing thermosetting prepregs: wet method and dry method: the wet method is to dissolve the resin in a low boiling point solvent for fiber impregnation, and then dry the solvent to volatilize the prepreg after impregnation, which has the advantages of simple equipment and convenient operation, but the ratio of fiber to resin is difficult to control, which affects the quality of the prepreg; the dry method is to melt the resin at high temperature and then impregnate the fiber, which has high control accuracy for the resin content, but the process is cumbersome and the temperature is not easy to control. The present invention adopts a new prepreg preparation process, disperses the unfoamed expanded microspheres in the glue, impregnates the chopped fibers and heats them for foaming, prepares them into foamed fiber felt, mixes the solid and liquid epoxy resins into liquid at a relatively low heating temperature according to the proportion, and impregnates the foamed fiber felt and cools and solidifies to prepare the prepreg, which can avoid the problem of resin matrix solidification caused by the excessively high foaming temperature of epoxy resin and hollow microspheres when they are directly mixed. In addition, the fibers in the foamed epoxy resin prepreg are evenly dispersed and distributed in an unoriented manner, which reduces the anisotropy of the material, has excellent comprehensive mechanical properties, and can replace traditional carbon fiber prepregs, effectively reducing costs. Compared with the prior art, the present invention has the following advantages and positive effects: The present invention uses micron-sized hollow microspheres as new material additives. When heated, the gas inside the microspheres expands and the volume becomes larger, which can significantly reduce the material density. The present invention adopts short-cut fibers instead of continuous fibers and is matched with an emulsion binder, so that the short fibers can be evenly distributed without orientation and the anisotropy of the material can be reduced. The present invention mixes foamed hollow microspheres with chopped fibers to avoid resin solidification due to excessively high foaming temperature, and more hollow microspheres can be added to reduce density, while allowing the resin to better infiltrate the fibers and improve material performance. DETAILED DESCRIPTION In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. Specific preferred examples are as follows: Embodiment 1: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:10:20, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:50, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 2: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:10:20, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. The emulsion glass fiber chopped strand mat is immersed in the aqueous emulsion prepared in S1, the excess emulsion is squeezed out by roller pressing and dried, and the hollow microspheres are rapidly foamed at 170°C to obtain a foamed emulsion glass fiber chopped strand mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 3: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:10:20, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:200, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 4: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:25:50, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:50, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 5: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:25:50, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 6: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:25:50, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:200, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 7: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:50:100, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:50, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 8: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:50:100, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Embodiment 9: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:50:100, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:200, and then cooled and solidified to obtain a foamed epoxy resin prepreg. In order to further illustrate the technical effect of the present invention, the present invention also provides a comparative example, which is as follows: Comparative Example 1: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:25:50, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:25, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Comparative Example 2: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:25:50, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:250, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Comparative Example 3: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:5:10, and disperse by high-speed shear stirring to obtain a uniform water-based emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Comparative Example 4: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:100:100, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. Comparative Example 5: A method for preparing a foamed epoxy resin prepreg comprises the following steps: S1. Add unfoamed hollow microspheres and water-based acrylic acid into water, the mass ratio of water, water-based acrylic acid and hollow microspheres is 100:75:150, and disperse by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immerse the chopped glass fibers in the aqueous emulsion prepared in S1, roll out the excess emulsion and dry it, heat it to 170°C to rapidly foam the hollow microspheres to obtain a foamed emulsion glass fiber chopped mat; S3. Add the curing agent dinitrile amine and the accelerator organic urea to the liquid epoxy resin, grind and disperse evenly, mix the liquid epoxy resin and the solid epoxy resin in proportion and heat to 80°C to dissolve, add the liquid epoxy resin with the curing agent and the accelerator and mix evenly, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:100; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, wherein the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:100, and then cooled and solidified to obtain a foamed epoxy resin prepreg. The prepregs in the embodiments and comparative examples were sealed in vacuum bags and then placed in an oven, heated to 150°C and cured for 20 minutes to prepare epoxy resin composite material specimens, which were tested for density, thickness, compression properties and shear properties. The results are shown in the following table. In summary, the material samples prepared in each embodiment of the present invention have low density and small thickness, which is conducive to lightweighting of the material. At the same time, the compression strength and shear strength are high, and the comprehensive mechanical properties are excellent.

Claims

1. A method for preparing a foamed epoxy resin prepreg, characterized in that: The following steps are involved: S1. The unfoamed hollow microspheres and aqueous acrylic acid are added to water, and dispersed by high-speed shear stirring to obtain a uniform aqueous emulsion glue; S2. Immersing the chopped glass fibers in the aqueous emulsion prepared in S1, rolling out the excess emulsion and drying, heating the hollow microspheres to rapidly foam, and obtaining a foamed emulsion glass fiber chopped mat; S3. The curing agent and accelerator are added to the liquid epoxy resin, ground and dispersed evenly, the liquid epoxy resin and the solid epoxy resin are mixed and heated to dissolve, and the liquid epoxy resin containing the curing agent and accelerator is added and mixed evenly; S4. The epoxy resin prepared in S3 is kept at a constant temperature and impregnated with the foamed emulsion glass fiber chopped strand mat prepared in S2, and then cooled and solidified to obtain a foamed epoxy resin prepreg.

2. The method for preparing a foamed epoxy resin prepreg according to claim 1, wherein: In the step S1, the mass ratio of water, aqueous acrylic acid and hollow microspheres is 100:10-50:20-100.

3. The method for preparing a foamed epoxy resin prepreg according to claim 1, wherein: The heating temperature in step S2 is 160-180°C.

4. The method for preparing a foamed epoxy resin prepreg according to claim 1, wherein: The curing agent in step S3 is dinitrile amide, and the accelerator is organic urea.

5. The method for preparing a foamed epoxy resin prepreg according to claim 1, characterized in that: The heating and dissolving temperature in step S3 is 70-90°C.

6. The method for preparing a foamed epoxy resin prepreg according to claim 1, characterized in that: In step S3, the mass ratio of the liquid epoxy resin to the solid epoxy resin is 100:50-150.

7. The method for preparing a foamed epoxy resin prepreg according to claim 1, characterized in that: In the step S4, the mass ratio of the epoxy resin to the emulsion glass fiber chopped strand mat is 100:50-200.

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